Gasoline hammer



Oct. 23, 1934. w ROBERTS I 1,977,645

GASOLINE HAMMER Filed Sept. 22. 1931 2 Sheets-Sheet 1 [knew/Jr Oct. 23, 1934. w ROBERTS 1,977,645

GASOLINE HAMMER Filed Sept. 22. 1931 2 Sheets-Sheet 2 ,6 ii 0 F2 5 25! @j J (ii Patented Oct. 23, 1934 UNITED STATES PATENT OFFICE My invention relates to that type of hammer or percussion drill in which the piston of a gasoline engine functions as the striking member. In the present invention, following the general 6 practice in gasoline hammers previously manufactured, there is embodied a gasoline engine of the two-cycle type. The piston, at the end of its outward or explosion stroke, operates to impact,

' either directly or indirectly, the end of a tool bit which may be a drill, chisel, tamper, riveting die or other tool.

The object of my invention is to accomplish what my experience has shown to be desirable attributes of a gasoline hammer. These are to so interconnect the piston, with its related mechanism that it may be propelled by the impulse of an explosion in the cylinder at the greatest possible speed; to avoid all possible retarding effect and cushioning of the blow before and at the 0 instant of impact; to provide means for returning the piston on the compression stroke, such means comprising a flywheel and accessory parts, the flywheel adapted to store kinetic energy for such purpose; transferring a portion of the energy of theexplosion to the flywheel during the explosion stroke; to provide for disconnection of the flywheel and its accessory parts from the piston at and immediately after the instant of impact that the energy of the recoil may be absorbed by the 0 piston and not transferred to other parts of the hammer; to make the energy of the recoil available to start the piston on the compression stroke. Other objects are to secure the above attributes with simple mechanism, and provide a combination that shall be sturdy and reliable.

In processing my invention, I employ a camshaft comprising a cam, with a flywheelfixed to the camshaft to return the piston on the compression stroke, and an anvil disposed between the piston and the tool bit. Ignition current is supplied by a flywheel magneto.

In the drawings: v

Fig. 1 is a sectional elevation of one form of gasoline hammer embodying my invention, the section taken along the line 1--1 of Fig. 2.

Fig. 2 is a sectional elevation of the hammer taken along the line 22 of Fig. 1.

Fig. 3 is an end or top view.

Fig. 4 is a-fragmentary section of the piston taken on the line 4-4 of Fig. 1, with the camshaft in the position it occupies in place in the hammer relative to the piston.

Fig. 5 is an elevation of the flywheel as it would be seen if viewed from the center of the cylinder, with the camshaft and the flywheel hub in section as if out along the line 55 of Fig. 1.

This view shows the position of the fan blades coil and the circuit breaker are illustrated with the parts shown detached.

Figs. 6 to 12 inclusive are diagrams illustrating the positions of the cam and the piston relative to one another and to the tool bit at successive 85 intervals in the rotation of the camshaft.

In the figures, the cylinder is designated by the numeral 13. Surrounding the cylinder is an outer or jacket wall 14, the space provided between this wall and the cylinder comprising an air-jacket space 15 through which air may be drawn to cool the cylinder walls. At intervals across the jacket space are ribs 16 providing longitudinal air spaces 15' which are that part of the air-jacket contiguous to the left-hand end of the cylinder in Figs. 1 and 2. At approximately the mid point of the cylinder there is provided a cylindrical compartment 17 which will be designated hereafter as the camcase. It is surrounded by the wall 18. 0

Bolted to that side of the cylinder which is uppermost in Fig. 1 is the by-pass cover 19, providing between the cover and cylinder 13 the semiannular space 20 corresponding to the by-pass or transferport common to the usual type of two-cycle engine. Attached to the by-pass cover, and registering with the passage 21 provided in the cover, is the mixing valve 22with the customary check valve 22. The gasoline supply tank 23 is bolted to by-pass cover 19 by bolts through lugs 24 welded to the tank.

Within-the cylinder 13, and operative to reciprocate axially therein, is the piston 25 having a deflecting plate 25 integral therewith. The piston is provided with two longitudinal slotstherethrough designated by numerals 26 and 27. The center planes of the slots are disposed at a right angle one to the other and the center planes extended include the axis of the piston. Through slot 26 is disposed the camshaft 28, two sides of bearing collar 29 being flattened to permit its passage through slot 26, the manner of this flattening being indicated in the view of the camshaft shown in Fig. 1. Attached to the camshaft, and preferably integral therewith, is the cam 30. While the particular contour shown in the drawings, with one side 'a circular arc and the otherside flattened, meets the requirements, I do not wish to confine myself to this particular cam contour. Cam 30 is so disposed in slot 27-that it is free to rotate therein. That portion of the piston which would otherwise lie between the slot 26 and the periphery of the piston 25 below the camshaft and to the right in Fig. 4 is cut away at the midpoint of the piston to permit assembly of the camshaft in place. Should the cam be made a separate piece frorn the camshaft, this portion may be allowed to remain. within the slot 27 is the roller 31, preferably mounted on a roller or a ball bearing. The roller is operative to contact with the cam during the inward or compression stroke of the piston. The thrust of the cam during the few revolutions required for starting the hammer when driving the piston on its outward stroke is taken by the righthand end of slot 26.

Attached to the side of camcase 17, attached to the cylinder at this point, is camcase cover 32 containing the ball bearing 33. This bearing and ball bearing 34 in the cylinder wall opposite cover 32 provide journals for camshaft 28. Mounted on the end of camshaft 28, and fixed thereto, is the flywheel 35 on which are fan blades 36, the blades preferably cast integral with the flywheel. Within the rim of the flywheel is mounted magnet 37 of the flywheel magneto. The circuit breaker 39 and the coil 38 belonging to the magneto are indicated in Fig. 4 in their positions relative to the contiguous parts but detached from plate 40 (Fig. 1) to which they are fixed. The circuit breaker and the coil have been omitted from Fig. 1 for the purpose of simplifying these drawings. Air entering jacket 15 by way of openings 15passes through the jacket to exit by way of ports 41 and 41 to the fan blades whence it is discharged to the atmosphere. Additional air enters through holes 35 provided in the web of the flywheel, to the magneto compartment provided between plate 40 and the flywheel, this air being drawn through the magneto compartment by fan blades 36.

Within the right-hand end (Figs. 1 and 2) of piston 25, there is provided a cavity 42 for the admission of shank 43' of anvil 43 which is slidably mounted within cylinder 13. The anvil is provided with a cavity 44, similar to that in the piston, for the admission of the end of the tool bit 45. The purpose of the cavities is to shorten the over-all length of the hammer while providing an ample longitudinal bearing surface for the piston and. the anvil. The end of the anvilv has an enlargement 46 fitted to the counterbore 47 provided in the cylinder. The purpose of this enlargement is to provide a shoulder to restrain the anvil from entering too far into the cylinder due to the thrust of the tool bit 45.

Cylinder head 48, bolted to the end of cylinder 13, is provided with a tapped hole for thereception of spark plug 49. Attached to the cylinder head, and preferably integral therewith, are handle lugs 50 into which are threaded handles 51. On the handles are grips 52, preferably of rubber composition, steam hose making a satisfactory grlp. I

At that end of the cylinder opposite that to which head 48 is attached is a second head 53 adapted to receive the end of tool bit 45. This head is yieldingly attached. to the cylinder 13 by means of bolts 54 and hook nuts 56 between which nuts and the flange of the head are disposed the springs 55. Loosely mounted in a hook bolt is link 57 adapted to retain the tool bit 45 in place in the head when the hammer is raised from the work. This particular tool retainer is Mounted commonly used in certain makes of air hammer, and other devices adaptable to the same purpose may be substituted therefore.

In the wall of cylinder 13 are provided three ports or openings therethrough. Port C provides communication between by-pass I20 and compartment 42. Inlet port I provides communication between that portion of the interior of the cylinder between piston 25 and the head 48, and by-pass 20. Exhaust port X provides communication between the interior of the cylinder and jacket space 15 through which the exhaust escapes with the cooling air by way of port 41 to the fan blades 36 and thence to the atmosphere. This method of disposing of the exhaust gases has'been.

found satisfactory in practice.

In the operation of my improved gasoline hammer, the general functioning is that of a twocycle engine of the two-port type in which engine the admission of the mixture to the crankcase is through a check valve. Starting the hammer by spinning the flywheel, the mixture is drawn into the by-pass and compartment 42 from mixing valve 22 by the inward stroke of the piston reciprocated by cam 30. Compartment 42 corresponds to the crankcase of the usual form of twocycle engine. On the outstroke of the piston check valve 22' is closed and the mixture is trapped in the by-pass and compartment 42, to be compressed therein. As the piston nears the end of its outward stroke, it uncovers port I admitting the mixture to the cylinder between the piston and head 48. The mixture is deflected by deflecting plate 25' toward head 48 to prevent it from passing across the end of the piston to exhaust port X. The mixture is compressed by the piston on its next inward stroke, and is ignited by a spark at spark plug 49. The resulting explosion impels the piston on its next outward stroke, the exhaust gas escaping through port X.

Referring now to the diagrams Figs. 6 to 12 inclusive the relative positions of the cam and the piston. at successive intervals in the rotation' of the cam will be described. In Figs. 6-12 the element struck by the piston may be the anvil shank 43 or the end of tool bit 45 either one since the relative positions of the parts would be that to the tool bit in case the bit were to be impacted directly by the piston instead of through an anvil. Cam 30 is designated by the letter K, the piston 25 by the letter P and the roller 31 by the letter R. All these parts are indicated by outline only. The direction of rotation of cam 30- (always clockwise) isdesignated by the curved arrows and the direction in which the piston is traveling at the time, by straight arrows. In Figs. 7 to 11, the position which would have been occupied by the right-hand end of the piston were it to be impelled by the cam alone is designated by a dot-and-dash line. In Fig. 9, the position of the end of the piston at the right, at the instant of impacting the tool bit, is designated by a dash line. The surface of the piston against which the cam will hear when it is impelling the piston on its outward stroke is designated by the letter S. The letter O in Fig. 9 designates the over-run or the distance the piston will travel under the impulse of an explosion beyond that which it would travel when impelled by the cam on the outward stroke.

In Fig. 6, the cam 30 is driving the piston 25 through the agency of kinetic energy stored in the flywheel 35, and is just completing the inward or compression stroke. It should be noted that while thepiston has reached its inner dead center position the half revolution of the cam corresponding to the inward stroke of the piston has not been completed. This is because of the location of roller 31 below the axis of piston 25.

In Fig. 7, cam 30 has passed its inner dead center position and roller 31 is bearing against the flat side of the cam, with piston 25 started on its outward stroke-impelled by the force of an explosion, this force indicatedby the arrows to the left of the piston. The roller is now functioning to impel the cam, and through the camshaft to turn the flywheel and store kinetic energy therein.

It should be noted, as this description progresses, how the piston 25, during its outward stroke, is free to move faster than it would if it were impelled by the cam 30 in contact with wall S which indicates the end of slot 26.

In Fig. 8, the cam has turned through an arc of about 48 since it has passed the inner dead center position, and the piston 25 is already in contact with the end of tool bit 45. Note that the right-hand end of the piston has progressed beyond the dot-and-dash line indicating the position it would assume at the end of the stroke when driven by the cam 30 in'contact with surface S.

In Fig. 9, cam 30 has turned through an arc of 90 since it has reached its inner dead center position. The tool bit 45'has been driven beyond the position it has been shown to occupy before impact in the previous diagrams. This distance designated by the letter F is the follow through. The follow through is limited by the distance, measured along the direction of piston travel, between anvil 43 and head 53 when the anvil is against the shoulder of counterbore 47. Note that this distance is neither the over-run nor the follow through, but is the distance which regulates both. If this distance is not properly adjusted, the hammer will not function satisfactorily. If the over-run is too great, the hammer will stop when lifted from the work. If it is too small, the hammer will run too slowly when the operator presses downward on the handles. This feature will be discussed later.

In Fig, 10, the cam 30 has turned through 45 from its position in Fig. 9, and the piston is recoiling from the tool bit 45.

In Fig. 11, the cam 30 has reached the end of the half revolution corresponding to the outward stroke of the piston 25. The piston has recoiled further from tool bit 45 but has not come into contact with the cam, which is about to contact with roller 31. Should the piston strike the cam as the result of T55 recoil, the drill will run too slowly when the bit is forced to the work. Adjustment to avoid this asdescribed under the commentson Fig. 9, can be made once and to all at the factory.

In Fig. 12, the cam 30 has started to drive piston 25 toward the head 48, bearing against roller 31. The cam continues to drive the piston on its compression stroke until the relative positions of the parts are as shown in Fig. 6, and the cycle has been completed.

In the sequence of relativepositions just described in connection with the diagrams, the relations between the parts are not illustrative of an imaginary or theoretical performance. The relative movements can be secured by adjustments of the relative positions of the cam and the roller together with that of the over-run, as well as by alterations in the contour of the cam.

In a gasoline hammer of the general type I have and the cam in contact with the roller by the described, it is possible to eliminate the anvil without disturbing the functioning of the ham mer, by the installation of packing around the end of the tool bit to prevent loss of mixture in the precompression chamber corresponding to compartment 42. v This would require that all tool bits be closely fitted into cylinder head 53. By the interposition of anvil 43, it is not requisite that the end of the tool bit be packed, and commercial forms of tool bit may be employed.

It has been found that gasoline hammers, built along the lines described, will run at speeds corresponding to 1,100 R. P. M. of the flywheel, reciprocating an eight or a nine pound piston. The over-run may be so adjusted as to give inherent regulation, the hammer slowing to about 400 R. P. M. when idling or when lifted from the work, and will speed up to 1,100 when the operator presses downward on the handles. This feature is brought about by the deadening of the recoil when the hammer is idling and striking the head 53 when lifted from the work. This is easily shown by the fact that with too great an overrun, the hammer will stop when lifted.

A hammer of this type will run when inclined 100 to any angle that will not interfere with the flow of the fuel from the tank to the mixing valve. Lubrication is secured by mixing oil with the fuel, sufficient oil passing the piston to effectively lubricate the bearings. I have picked such a hammer a cylinder, a piston axially reciprocable therein, 11() the piston provided with two slots therethrough,

a tool bit slidably mounted in one end of the cylinder, a camshaft journalled in the cylinder, a cam on the camshaft, a roller on the piston, the roller in a slot, the cam in the slot with the roller, the camshaft disposed through the second slot, the piston operative to rotate the camshaft, the camshaft operative to reciprocate the piston, a flywheel on the camshaft and fixed thereto, the aforesaid combination operative to function as a gasoline engine of the two-cycle type, wherein the piston is adapted to impulsion by the force of an explosion in the cylinder, the flywheel operative to return the piston during the compression stroke through kinetic energy stored in the flywheel during the explosion stroke, the conformation of the cam such as to permit the piston to move axially at a greater rate of speed than if it were driven by the cam, and to strike the tool bit unrestrained by the cam.

2. An explosion engine operative to function as a hammer having in combination a cylinder, 2. piston axially reciprocable therein, a tool bit slidably mounted in one end of the cylinder, an anvil block in the cylinder between the piston and the tool bit, the anvil block slidable in the cylinder, a camshaft journalled in the cylinder, a cam on the camshaft, the piston provided with slots therethrough, a roller on the piston, the cam and the roller disposed in the same one of the slots, the camshaft disposed through a second slot, a, flywheel fixed to the camshaft, the piston operative to impact the tool bit through the anvil block when impelled by an explosion in the cylinder, the piston operative to rotate the camshaft and the flywheel through the medium of the roller and the cam, the flywheel operative to return the piston through the medium of the camshaft motivating means of kinetic energy stored in the flywheel during the explosion stroke.

3. In a hammer comprising an explosion engine of the two-cycle type, the combination of a cylinder, a piston axially reciprocable therein, the piston provided with two slots therethrough, a camshaft journalled in the cylinder, a cam on the camshaft, the cam in a slot, a roller on the piston in the same slot with the cam, the camshaft disposed through the second slot, the cam adapted to reciprocate the piston through the roller in one direction and in contact with the end of the first slot in the opposite direction, the piston adapted to impulsion by an explosion in the cylinder during the outward stroke, the piston operative to turn the camshaft through the roller and the cam, a flywheel fixed to the camshaft to turn therewith, and kinetic energy stored in the flywheel from an impulse of an explosion on the piston operative to return the piston during the compression stroke.

4. In a hammer comprising a gasoline engine of the two-cycle type, the combination of a cylinder, a piston axially reciprocable in the cylin der, the piston provided with two slots therethrough, the slots disposed at a right angle one to the other, the slots lengthways of the piston, a camshaft journalled in the cylinder, a cam on the camshaft, the cam in one slot, the camshaft disposed through the second slot, the rotation of the camshaft operative through the cam to reciprocate the piston, the piston adapted to'impulsion by an explosion in the cylinder, the impulsion operative during the outward stroke of the piston, the piston operative to turn the camshaft through the cam, a flywheel fixed to the camshaft, energy stored in the flywheel during the outward stroke of the piston operative to return the piston on the compression stroke, a tool bit slidably mounted in one end of the cylinder, and the piston operative to impact the tool bit at the end of the explosion stroke.

5. In a hammer comprising an explosion engine, the combination of a cylinder, a piston reciprocable therein, the piston provided with two slots therethrough, the slots disposed at a right angle one to the other, the slots lengthways of the piston, a camshaft journalled in the cylinder,

a cam on the camshaft, the cam in one slot, the camshaft disposed through the second slot, rotation of the camshaft operative through the cam to reciprocate the piston, the piston adapted to impulsion by an explosion in the cylinder during the outward stroke, the piston operative to turn the camshaft through the cam, a flywheel fixed to the camshaft, the flywheel operative to return the piston on its inward stroke due to energy stored in the flywheel during the explosion stroke, a tool kit slidably mounted in one end of the cylinder, an anvil block slidably mounted in the cylinder between the piston and the tool bit, the piston adapted to impact the anvil at the end of the explosion stroke and the anvil operative to transmit the force of the impact therethrough to the tool bit.

6. In a gasoline hammer, the combination with a cylinder of a jacket wall surrounding the cylinder and disposed at a distance therefrom, the space provided between the jacket wall and the cylinder providing an air space adapted to the passage therethrough of air to cool the cylinder, a camshaft journalled in the cylinder, a flywheel fixed to the camshaft, fan blades fixed to the 10 flywheel, a magneto incorporated in the flywheel, and the fan blades operative to draw air through the air space surrounding the cylinder and through the compartment provided for the magneto.

7. In a gasoline hammer comprising an explosion engine having the customary cylinder with a piston reciprocable therein, the combination therewith of a camshaft journalled inthe cylinder, the axis of the camshaft disposed at a right 11 angle to the axis of the cylinder, a cam on the camshaft, a flywheel fixed to the camshaft, the camshaft operative to reciprocate the piston, the piston operative to turn the camshaft when impelled by an explosion in the cylinder and during 115 the outward stroke of the piston, the turning of the camshaft by the piston operative to store kinetic energy in the flywheel, and the flywheel operative through the camshaft and the cam to return the piston on the inward stroke by the expenditure of kinetic energy stored in the flywheel.

EDMUND W. ROBERTS. 

